In the field of document processing in which a large quantity of documents are processed collectively, documents are generally processed in accordance with document images to which pieces of processing control information permanently set for the respective types of documents, i.e., information indicating specific positions of documents at which character recognition is to be performed, information indicting specific areas of documents from which information is to be extracted, and the like, are input.
In consideration of physical errors in a read mechanism and instability of paper documents themselves, it is almost impossible to read a large quantity of document images one by one accurately at the same position by using a scanner. This tendency has recently become increasingly conspicuous with an increase in the processing speed of scanners.
When processing is to be performed on the basis of permanent positional information in this situation in the above manner, a decrease in the precision of subsequent processing, e.g., character recognition, due to a positional offset is inevitable.
Conventionally, to prevent such a problem, positioning markings are formed on documents themselves to obtain the reference position of each document, and various processes are performed on the basis of the position of a predetermined processing target area relative to the reference position. Alternatively, the layout of a document itself is designed to set a large margin for a positional offset, or a high-resolution scanner is used.
The conventional document positional offset preventing method described above is subjected to strict constraints concerning document design. A high-resolution scanner leads to an increase in cost. These factors have greatly interfered with efficient document processing. Another serious problem is that it is almost impossible to apply this method to read processing systems for processing different types of documents, which tend to become mainstream.
The present invention has been made in consideration of the above problem, and has as its object to correct the positional offset of an image without performing any processing for the setting of a reference position with respect to a document image, e.g., the setting of markings.